1. Field of the Invention
The present invention relates to an image forming apparatus for forming a polymer image including the polymer disposed in an image pattern, on a photosensitive image forming member (referred to merely as "image forming member" hereinafter).
2. Related Background Art
An image portion and a non-image portion of a polymer image have different properties of matter such as wetness and/or adhesion in accordance with the difference in the degree of polymerization and/or of bridge formation, and, therefore, the polymer image has widely been utilized as a means for forming a color image. While various methods for forming such polymer images are already known, generally, the silver salt or a metal mask is used to obtain a printed board, photoresist and the like and the photopolymerization is effected by means of a light source such as a mercury lamp having strong light intensity to form the polymer image.
However, since such method requires complex processes such as a liquid treatment process because of the presence of the silver salt or the metal mask, there arise drawbacks that it requires much labor and time and that the whole system becomes bulky.
Various improvements have been tried to simplify such method and to perform such method with the complete dry treatment processes. For example, as disclosed in the Japanese Patent Laid-Open Nos. 61-75342, 55-50246 and 62-17155 (corresponding to U.S. Ser. No. 302,270 filed on Jan. 27, 1989 in U.S.A), there has been provided a method wherein, after the photosensitive material made of at least photosensitive silver halide, organic silver salt, reducing agent and the like is exposed (image exposure process), the reaction is caused (heating process) by applying heat at a heat developing portion, thereby affording the polymerization prohibiting ability and light-shielding ability to the produced, quenched or decomposed substances, and thereafter, the polymerizing and bridging reaction is caused by light at a whole image exposure portion (whole image exposure process) to form the polymer image.
The method for forming the polymer image by utilizing the photopolymerization reaction as mentioned above takes an advantage that each reaction in each process can be easily controlled, thus providing an image with high resolving power and high contrast, because in such method, a plurality of chemical reactions are not concurrently progressed (unlike the heat polymerization reaction), but each chemical reaction is effected in each process.
However, in such an image forming apparatus using the dry treatment process, the whole image exposure treatment is inevitably required for effecting the polymerizing and bridging reaction by the light with respect to the image forming member passed through the heat developing portion.
As a light source used with the whole image exposure treatment, a mercury lamp or a fluorescent lamp for emitting ultraviolet radiation is used for forming the polymer image by the ultraviolet radiation. When the fluorescent lamp is used, it is necessary to reserve an adequate axial room for avoiding the arrangement of the filament at both ends of the lamp and a surrounding space for arranging a reflection plate and the like. On the other hand, when the mercury lamp is used, a lens for condensing the light from the lamp and a cooling system for the lamp are inevitably required, thus making the whole light source bulky. Thus, the whole image exposure portion requires a relatively large installation space, leading to a problem that the whole image forming apparatus becomes large-sized
Further, in order to prevent the occurrence of the fog area on the image forming member, the light from the whole image exposure portion must not be illuminated on the image forming member until the heat development regarding the image forming member has been completed. Accordingly, in order to prevent the leak of light from the whole image exposure portion to the heat developing portion, different light-shield means must be provided both at the image exposure portion and at the whole image exposure portion. Particularly, in an area where the image forming member is fed through such light-shield means, the construction of the light-shield means of the whole image exposure portion becomes complex, thus arising a problem that the reliability of the light-shield means is worsened.
Among the above-mentioned image forming apparatuses, the apparatus using the liquid treatment process arises problems that it takes a long time for forming the image and that the whole apparatus becomes bulky.
On the other hand, in the apparatus using the dry treatment process, since the installation space for the whole image exposure portion is increased, there arise problems that the whole apparatus becomes bulky and that the light-shield means for preventing the leak of light from the whole image exposure portion to the heat developing portion becomes complex and the reliability of the light-shield means is worsened.